The olefin polymer is generally excellent in mechanical properties, and hence has widely been employed in varied fields such as ones of molded products of all sorts. However, since the demands for physical properties of olefin polymers have been diversified recently, olefin polymers with various properties have increasingly been desired.
As an example of olefin polymers satisfying such demands, known is a polar olefin copolymer obtained by copolymerizing a non-polar olefin and a polar olefin to provide properties which cannot be expected in a polymer consisting of non-polar olefins only. Radical polymerization method is well known as a conventional process for producing a polar olefin copolymer by copolymerizing a non-polar olefin and a polar olefin, and for example, ethylene-vinyl acetate copolymers and ethylene-acrylic ester copolymers have been produced by this method.
In producing a polar olefin copolymer by the radical polymerization method, reaction conditions at a high temperature and under high pressure are often required. In view of such circumstances, there has been desired a process capable of producing a polar olefin copolymer under more moderate conditions.
As a process for producing a polar olefin copolymer under less strict conditions than the conventional ones, the process for copolymerizing a non-polar olefin and a polar olefin using a transition metal complex catalyst has been reported recently. For example, Brookhart et al. disclosed a process for producing a copolymer of a non-polar olefin such as ethylene and methyl acrylate under moderate conditions using a diimine complex of palladium (J. Am. Chem. Soc. 1998, 120, 888 etc.). There are only a few cases, however, in which a non-polar olefin and a polar olefin have been copolymerized by using a transition metal complex catalyst, and the kinds of polar olefins employable to be copolymerized are still limited.
In the above situation, there has been desired the development of a process for producing a polar olefin copolymer which is superior in the capacity for copolymerizing a polar olefin and capable of obtaining a polar olefin copolymer with excellent properties.